1. Field of the Invention
The present invention relates to a hammer drill including a clockwise and counterclockwise driven tool spindle, a drive pinion operatively connectable with the tool spindle for transmitting a torque thereto, a separate control handle for selecting one of drill functions including a pure drilling operation, a pure percussion operation, and a drilling or rotary and percussion operation, and a switching device adjustable in accordance with the position of the control handle.
2. Description of the Prior Art
Hammer drills of the type described above are very operator-friendly because switching between all three drill functions with the same control handle is possible. Moreover, the control handle can be easily arranged in such a way that switching of the drill functions takes place at an easily accessible and well visible location.
German Publication DE-195 45 260 discloses a hammer drill in which switching between a pure drilling operation, a rotary-percussion operation, and a pure percussion operation is effected with a single rotary switch. The rotary switch is connected with a rotatable body for joint rotation therewith. The rotatable body displaces a shifting bushing arranged on an intermediate shaft and shifting sleeve arranged on the tool spindle. The percussion mechanism of the hammer drill is actuated and deactuated dependent on the position of the shifting bushing. Simultaneously, dependent on the position of the shifting sleeve, the tool spindle rotates or is secured to the housing without a possibility of rotation. Further, the hammer drill has an actuation member which is provided on an on-off switch and which serves for switching between clockwise and counterclockwise rotation of the tool spindle by changing the polarity of the drive motor.
The drawback of the known hammer drill consists in that a separate switch should be provided for effecting the clockwise and counterclockwise operations and which is poorly visible. Further, in such a hammer drill, because of two rotational directions of the motor, the fan likewise should be adapted for operation in opposite directions. This reduces the power of the fan and thereby its cooling effect.
Accordingly, an object of the present invention is to provide a hammer drill in which the drawbacks of the known hammer drill are eliminated and the operating convenience is increased.